Known communication systems transfer either current or voltage between the communicating devices. Basically, a transmitting device sends data serially, by a series of voltage, or current, levels, which the receiving device decodes. Such a system requires a single wire per data transfer channel. If it is desired to communicate bidirectionally (in full duplex mode), two wires must be provided, one for each direction.
It is also known to use modulation techniques, such as time or frequency division multiplexing in order to have bidirectional communication over a single wire. However, these techniques require a modulator and a demodulator at each end. Such modulator/demodulators (modems) are usually relatively complex and require special filters and higher bandwidths, which lowers the noise immunity of the system.
It is therefore an object of the present invention to provide a bidirectional communication system which overcomes, or at least reduces, the disadvantages of known systems.